1. Technical Field
The present invention relates generally to preforms used in the construction industry. In particular, the present invention discloses preforms and methods for using the same to prevent concrete from entering the pipe installation areas when pouring concrete slabs.
2. Background Art
In the construction of residential and commercial complexes, pipes or conduits are used for several purposes such as plumbing, electrical and gas lines, heating, and disposing garbage. Pipes or conduits are installed in the ground prior to the pouring of concrete slabs. The area around, above and below these pipes and conduits typically constitute the space required to be maintained open for accommodating the pipes or conduits as well as for installing other devices such as floor sinks and garbage chute repositories.
Traditionally, these openings were kept free of concrete by manually building a brick structure around the predefined spaces. Concrete was then poured around the brick structures and after hardening of the concrete, the brick structures were destroyed. However, this process entailed additional labor time. Also, at times, the destroyed bricks were rendered no further use; thus adding to construction costs.
Therefore, preforms were developed and are widely used nowadays to maintain a concrete-free area around, above and below plumbing and other conduits. The preforms are designed with a perspective of lowering the labor time and cost associated with the formation of structures around the openings maintained for plumbing and electrical conduits and the like.
The conventional preform is fabricated from lumber, on site. The worker will take lumber, sometimes scrap lumber lying around the jobsite, and saw, hammer and nail the lumber into a box-like wooden preform structure of suitable size and shape. The completed wooden preform is set down in place around the pipe or other conduit protruding from the soil. The preform is then secured in place using wooden or metal stakes that penetrate the preform and also the soil directly below the preform. After the concrete is poured and allowed to cure, the sides of the preform are removed, rendering the lumber unusable thereafter and sacrificed.
However, this manner of constructing wooden preforms ad hoc on the jobsite adds unnecessarily to the cost of construction. Typically the time to construct a single blockout preform may be a half hour or more. This time takes the carpenter away from other tasks requiring carpentry skills. There is, in addition, the expense of the lumber used in the preforms and the risk of injury to the worker in fabricating the preform on-site.
Accordingly, it is a primary object of the instant invention to provide an apparatus and method for forming preforms for concrete blockouts that avoid the time, expense and risk of injury consequent to having to fabricate wooden preforms on site in advance of a concrete slab being poured.
Often, the soil under the construction slab is prepared using insecticides and/or pesticides. The pesticide treated soil is then covered with a moisture/vapor barrier material, such as treated plastic sheets. The barrier is laid down over the soil prior to the pouring of the slab. The soil treatment and barrier come with warranties. These warranties are relied upon by the contractor constructing the building, and also by the owner of the finished building, for protection against the later infiltration of pests and moisture. The use of the stakes to secure the wooden preforms to the soil, penetrates the soil and the moisture barrier materials and voids the warranties that accompany these materials and treatments.
It is a further primary object of the present invention to provide an apparatus and method for creating concrete blockouts in order to preserve openings around, above and below plumbing and other conduits during the process of pouring concrete construction slabs, that do not compromise the moisture/vapor barrier below the slab and the warranties that accompany the treated soil and moisture barrier material.
It is not uncommon when using wooden site-constructed preforms that poured concrete will overtop the preform and/or seep through cracks in the preform, resulting in concrete seeping into the opening that the preform was intended to maintain material free. When this occurs, it becomes necessary to chip away at the unwanted hardened concrete from the pipe and out from the void that was to have been maintained below slab grade. Removing the unwanted concrete can be time consuming and not-uncommonly results in damage to the adjoining slab.
It is a further primary object of the present invention to provide an apparatus and method for forming concrete blockouts that effectively prevent composite materials from seeping into the void to be maintained around pipes and other conduits or from filling the space below slab intended to be maintained open for plumbing fixtures such as floor sinks.
The patent prior art discloses a variety of preform apparatus that serve to preserve openings around and below plumbing fixtures and conduits during the pouring of concrete slabs. The pre-fabricated preforms come in a variety of forms, are made from different materials, and function differently.
U.S. Pat. No. 1,391,988 to Zents, for example, discloses a mold for forming spaces in concrete floors to receive pipes for heating and plumbing. The mold comprises two sections fitted together and is meant to be easily removable and reusable. The mold has a cover which can be rotated to loosen the mold from the concrete. The mold is attached to the floor framework using a bolt that extends through the floor slab into the ground.
U.S. Pat. No. 2,684,518 to Whitlock discloses a device for forming openings in concrete slabs for utility conduits and outlets. The device comprises a male sleeve telescoped inside a female sleeve, with the male sleeve having a securing flange that is nailed into the concrete form. The male sleeve with flange is removed after the slab is poured. A concrete plug is formed at the opposite end of the device that can be punched out later to make way for the pipe or conduit. The female sleeve remains inside the slab after the pour.
Also, U.S. Pat. No. 3,821,338 to Faust teaches a sleeve protector to prevent wet cement from entering the sleeve, with a large flanged bottom plate that is nailed to a plywood deck. The sleeve protector includes radially spaced apart set screws to space the sleeve protector from the centrally located pipe or conduit. A cover plate is placed on top of the sleeve protector to prevent entry of concrete into the sleeve.
These prior art preforms make the use of fasteners necessary for attaching the preform to the floor or to their component parts or both. When such devices are used on slab-on-grade foundations, the fasteners penetrate into the soil thus piercing the vapor barrier and disturbing the treated soil. Furthermore, assembly/disassembly of different parts of these devices is complicated; thus increasing the assembly/disassembly time. Also, the complexity and materials used in the prior art preforms render them expensive to produce, provided little advantage over the conventional wooden preforms described above that are fabricated on site.
There is a need for an easy-to-use, ready to assemble preform that is inexpensive to produce, quick to assemble and disassemble requiring little effort, is simple with a minimum of parts, does not require fasteners, and does not require penetration of the treated soil or compromise of the moisture/vapor barrier.